1. Field of Invention
The present invention relates to a control method of an assist pump for automatic transmission of a vehicle provided with an ISG system. More particularly, the present invention relates to a control method of an assist pump for automatic transmission of a vehicle provided with an ISG system which may reduce electric power consumption and enhance battery durability and fuel efficiency.
2. Description of Related Art
Since demand for low fuel consumption vehicles has been increase, an ISG (Idle Stop and Go) system is in the spotlight of consumers as enhancement of fuel consumption.
If a vehicle provided with the ISG system stops and predetermined conditions are satisfied, an engine stops so as to reduce fuel consumption in idle state. The ISG system determines whether an engine stops or not considering battery system information, engine and transmission system information driver's control will and so on.
In the case of an automatic transmission, when an engine stops, a hydraulic pump system does not operated. And thus if rapid restart after engine stops is required, hydraulic pressure is not generated so that shock may occur. And thus generally an assist hydraulic pump is provided to a vehicle with an automatic transmission to maintain hydraulic pressure within the transmission.
In the case of a general ISG system for an automatic transmission, when an engine stops, an assist hydraulic pump of a transmission is operated, and when an engine re-starting is completed, operation of the assist hydraulic pump stops.
Flux supplied by the assist hydraulic pump is controlled according to the revolutions per minute RPM of the assist hydraulic pump, and an ECU (engine control unit) receives temperature signal of transmission oil and determines RPM based on one-dimensional table and then the ECU transmits CAN signal to an inverter of the assist hydraulic pump to control the assist hydraulic pump.
In the case of a general control method of a transmission assist hydraulic pump, if an engine stops, the transmission assist hydraulic pump is operated according to transmission oil temperature regardless of gear shift and engine stop period, and thus generated hydraulic pressure is more than necessary.
And also, when the assist hydraulic pump is operated and the engine stops, generation of electricity does not executed, and thus excessive load is applied to a battery and durability of the battery may be deteriorated.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.